The general goal of this program is the evaluation of clinical cardiac transplantation as a therapeutic procedure. Specific scientific objectives are directed toward developmet and refinement of techniques to maximize postoperative survival, and include: 1) definition of clinical criteria for selection of potential cardiac recipients and assessment of the impact of various clinical, physiological, and psychosocial factors present preoperatively on recipient survival and rehabilitation after transplantation; 2) correlation of histocompatibility typing and recipient immunological responsiveness with postoperative rejection history and survival; 3) the development of techniques for postoperative assessment of host immune responsiveness, diagnosis of graft rejection by direct histological assessment with transvenous endomyocardial biopsy, and correlation of kinetic data relating to treatment with rabbit antihuman antithymocyte globulin with postoperative rejection parameters; 4) the identification and management of psychological and social stresses associated with transplantation; 5) definition of postoperative hemodynamic and electrophysiological properties of the transplanted human heart, responses to various pharmacological physiological interventions, and the functional and anatomical changes associated with late postoperative complications such as graft arteriosclerosis. In addition, the clinical cardiac transplantation program provides in-depth training to both medical and sugical trainees in clinical and investigational aspects of heart transplantation. Furthermore, it constitutes a demonstration project in heart transplantation on both national and international levels.